Occupational Medicine & Health Affairs
Maeda and Nakano, Occup Med Health Aff 2013, 1:1
http://dx.doi.org/10.4172/omha.1000102
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Systolic Fetal Heart Murmur Detected in Fetal Phonocardiography
Kazuo Maeda1* and Hitoo Nakano2
1
2
Department of Obstetrics and Gynecology, Tottori University Medical School, Yonago, Japan
Department of Obstetrics and Gynecology, Kyushu University Faculty of Medicine, Fukuoka, Japan
Abstract
Although clear fetal heart tones were auscultated with high-pitched tones, a sinusoidal fetal heart rate (FHR)
was unable to be diagnosed, thus it was concluded that no fetal heart tone auscultation was suitable for the fetal
monitoring. Fetal heart systolic period was stable and the diastolic duration varied when the FHR changed. FHR
curve was traced with the triggers formed by single negative signal from the two tones of heart sound in the
instantaneous FHR meter, of which microphone touching noise in FHR curve was prevented using autocorrelation
heart rate meter, which made the automatic computerized FHR diagnosis successful. Fetal phonocardiography
(fPCG) was studied by the tracing of fetal heart tones with the high-pass and low-cut frequency character. The
oscilloscopic image recorded on a photographic film and the ink-writing record with slow-down tape technique using
a data recorder achieved the recognition of high frequency component of fetal heart sound. The fetal heart tones of
105 normal pregnancies were studied and diamond shaped 100-200 Hz systolic murmur was recorded in 16.8% of
the cases, which was not recorded and no cardiac abnormality was realized in the neonates after birth. Continuous
wave ultrasonic record did not realize the murmur, therefore, the murmur was considered physiologically developed
by the blood flow of fetal ductus arteriosus limitedly in antenatal life.
Keywords: Fetus; Heart sounds; High pitched listening; Fetal
monitoring; Phonocardiography; Systolic murmur; Ductus arteriosus.
Background
The electric fetal heart activity was firstly recorded as tiny deflections
on maternal limb lead electrocardifogram (ECG) by Cremer [1], direct
lead fetal ECG with needle electrode by Caldeyro-Barcia et al. [2] and
with scalp lead clip electrode by Hon [3]. Indirect maternal abdominal
lead fetal ECG (fECG) was recorded by Maeda and Nakano [4] and
others. Intrapartum fetal heart rate (FHR) was monitored by Hon [3]
and Caldeyro-Barcia et al. [2] using direct lead fECG. Hammacher and
Gentner [5] and Maeda [6] invented external FHR monitoring with
fetal heart sound for the full fetal monitoring in 1960s. High pitched
fetal heart sound listener and the fetal phonocardiography (fPCG)
were studied by Maeda et al. [7] before the introduction of ultrasound
diagnosis of the fetus in Japan.
Methods
Augmented fetal heart sound auscultation
A sensitive low impedance (8 ohms) dynamic microphone was
A
B
connected to the step-up transformer and transistor amplifier with
the peak at 60 Hz. The large corn speaker radiated low frequency fetal
heart sound, of which frequency was, however, too low to listen, and
disturbed by howling. Hence, the author used high pitched fetal heart
sound listening device, where 1.2 kHz oscillation was modulated by
low 60Hz fetal heart sound and the output was a small corn dynamic
speaker (Figure 1).
Fetal phonocardiography (fPCG)
The fetal heart sound shape was studied by its records using adult
standard microphone, hand-made amplifier and various recorders. The
oscilloscopic image record the highest frequency range of heart sound,
but needed to record with a film camera, and the record was studied
after processing the film. Heat-pen or ink-writing recorder was easy to
handle, but the high frequency was poorly recorded. The problem was
solved by a slow-down tape technique, where the signal was recorded
with TEAC R-400 data recorder (TEAC, Tokyo, Japan) with 30 in/s tape
speed, and the recorded tape was reproduced with 3 in/s tape speed,
where a high frequency signal was slow down to low frequency signal
and recorded by the heat-pen or ink-writing recorder (Figure 2).
Fetal systolic murmur in normal fetuses
Stethoscope listening detected no fetal heart murmur. High
frequency murmur was recorded with oscilloscopic fetal heart tone
image with photographic film (Figure 3), or ink-writing or heat-pen
*Corresponding author: Kazuo Maeda, Department of Obstetrics and
Gynecology, Tottori University Medical School, 3-125, Nadamachi, Yonago,
Tottoriken, 683-0835 Japan, E-mail: [email protected]
Figure 1: A: An oscilloscopic image of high-pitched fetal heart tones
recorded on 35 mm film with a photographic camera. The 1.2 kHz oscillation
was modulated by the 60 Hz fetal heart sound vibration.
B: The sinusoidal FHR existed in the high-pitched heart sound was recorded
and realized by the processing of tape-recorded high-pitched tone by a FHR
monitor (TOITU, Tokyo) long after its listening. The sinusoidal FHR produced
by fetal heart sound was not detected during listening to the high-pitched
clear fetal heart sound.
Occup Med Health Aff
ISSN: OMHA an open access journal
Received January 08, 2013; Accepted February 04, 2013; Published February
06, 2013
Citation: Maeda K, Nakano H (2013) Systolic Fetal Heart Murmur Detected in Fetal
Phonocardiography. Occup Med Health Aff 1: 101. doi:10.4172/omha.1000102
Copyright: © 2013 Maeda K, et al. This is an open-access article distributed under
the terms of the Creative Commons Attribution License, which permits unrestricted
use, distribution, and reproduction in any medium, provided the original author and
source are credited.
Volume 1 • Issue 1 • 1000102
Citation: Maeda K, Nakano H (2013) Systolic Fetal Heart Murmur Detected in Fetal Phonocardiography. Occup Med Health Aff 1: 101. doi:10.4172/
omha.1000102
Page 2 of 3
single trigger was constructed from the first and second tones of fetal
heart sound in a heart beat. Hammacher and Gentner [5] solved the
problem by an algorithm and by flip-flop multivibrator by Maeda [6].
Since common cardiotocogram (CTG) studied by fetal heart
sound accompanied the cloth touching noise of microphone, the
autocorrelation FHR meter was applied to the CTG to obtain a clear
noiseless tracing, and therefore it made the automated FHR diagnosis
successful using fetal heart sound [7]. The beat-to-beat FHR difference
was continuously recorded by fetal heart sound to study short term
variability using the beat-to-beat intervals between the first vibration of
the first heart tone in the instantaneous FHR meter (TOITU, Tokyo). It
needed delicate manual control of the input level but it was possible to
record the beat-to-beat variability [8].
Results
High pitched fetal heart sound listening device
Figure 2: A fetal phonocardiogram recorded with abdominal lead fetal ECG.
Microphone was modified TY-301 (Fukuda electrics, Yokyo), Slow down tape
output for 1/10 was recorded by San-Ei v-20 ink writing recorder. No fetal
heart murmur was recorded in the case of the late stage of pregnancy.
Although the high pitched fetal heart sound of I and II tones were
easily listened, recorded by common tape recorder, and transmitted by
telephone line, but the listening was unable to detect sinusoidal FHR
which was confirmed later by the processing of its tape recorded tone
with a fetal heart rate (FHR) monitor (Toitu, Tokyo) (Figure 1), thus
fetal heart auscultation did not apply to monitor the fetus to detect FHR
abnormalities.
Fetal systole and diastole
The systolic duration was almost constant, and the diastolic
duration was variable in the brady- or tachycardia. (Tables 1 and 2)
Systolic fetal heart murmur
Figure 3: A case of systolic fetal heart murmur (arrows) detected by modified
adult standard TY-301 microphone (Fukuda Electronics, Tokyo). It is an
oscilloscopic image photographed by a film camera. Neither murmur nor
heart abnormality was detected in the neonate after normal delivery.
Figure 4: Fetal heart murmurs (arrows) recorded by hand-made amplifier
(Maeda, hand-made) using 200 Hz peak, -18 dB/Oct filter, 1/5 slow-down
tape technique and an ink-writing recorder (SANEI V-20, Tokyo). The
murmur disappeared and no cardiac abnormality was noted in the neonate
after the birth.
the slow down tape technique using the recorder (Figure 4). The fetal
systolic murmur was detected in 16.8% of normal late stage pregnancy.
FHR monitoring with fetal heart sound
Although the FHR was initially recorded by direct lead fECG
obtained by the scalp electrode was using instantaneous FHR meter,
it was unable to trace the FHR during pregnancy and in early stage of
labor before the rupture of membrane. Therefore, fetal heart sound on
maternal abdomen was applied to trace the FHR with instantaneous
FHR meter by Hammacher and Gentner [5] and Maeda [6], where
Occup Med Health Aff
ISSN:OMHA an open access journal
The murmur was diamond shaped and composed of 100-200 Hz
vibrations during the systole between the first and second tones. The
murmur was recorded in 16.8% cases of normal fetuses, and neither
murmur nor heart abnormality was detected in the neonates after the
delivery, whose fetuses exhibited systolic murmur (Figures 3 and 4).
Comments
Although clear fetal heart tones were listened by the high-pitched
fetal heart sound listening device and its tones were easily recorded by
the common tape recorder and transmitted by telephone line, the tone
could detect only continuous brady- or tachycardia, but no transient
FHR change, no sinusoidal FHR or no LTV change, where the FHR
tracing obtained by the CTG recorded by the processing of reproduced
fetal heart sound just detected valuable FHR changes. Therefore, simple
auscultation of fetal heart tones should not be used in fetal monitoring
even in low risk cases, where the possibility exists to produce abnormal
FHR caused by sudden changes of umbilical cord, placenta or fetal
environments. It was remarkable that a beat-to-beat difference was
detected by fetal heart tones by the instantaneous FHR meter and the
beat-to beat FHR difference recorder [8].
Systole (start of I tone to that of II tone) 0.196 ± 0.020 sec (0.176 to 0.216 sec)
Diastole (II start to next I start)
0.221 ± 0.028 sec ( 0.193 to 0.249 sec)
Beat to beat interval (I to next I)
0.408 ± 0.038 sec (135 to 162 bpm)
Table 1: Durations of systole, diastole, beat-to-beat changes of fetal heart sounds.
FHR (bpm)
Systole (ms)
Diastole (ms)
136
180
260
100
180
420
Table 2: Durations of fetal systole and diastole according to the FHR change.
Volume 1 • Issue 1 • 1000102
Citation: Maeda K, Nakano H (2013) Systolic Fetal Heart Murmur Detected in Fetal Phonocardiography. Occup Med Health Aff 1: 101. doi:10.4172/
omha.1000102
Page 3 of 3
Fetal heart tone was composed of the first (I) and second (II) tones.
Therefore, FHR counted by simple application of fetal heart sound
would be twice of true FHR. The systole, however, almost stable in the
fetal phonocardiogram, therefore, the FHR was recorded using single
trigger signal produced by flip-flop multivibrator [8].
in automatic FHR diagnosis. Although fetal systolic murmur detected
in the fPCG was physiologic in our cases because it disappeared after
the birth and no cardiac abnormality was found in the neonate, fetal
heart murmur may be a positive screening sign of congenital heart
disease.
The cloth touching noise to microphone disappeared by the
application of autocorrelation FHR meter applied to automatic
diagnosis of abnormal FHR with computerized analysis [7]. Fetal
systolic murmur was recorded by fPCG in many fetuses, who showed
neither neonatal heart murmur nor neonatal cardiac abnormality. Since
cardiac murmur is the sign of cardiac abnormality in adult patients,
fetal heart murmur was also warned to be the sign of abnormal fetal
cardiac function [9]. Postpartum disappearance of the systolic murmur
detected during antepartum fPCG would be caused by particular
fetal circulation, e.g. the blood flow in the ductus arteriosus will
develop the systolic murmur, because the blood may flow ductus
arteriosus in the systolic phase, the Doppler flow signal in the ductus
arteriosus disappears within 48 hours after births in normal neonates
[10], and neonatal persisted ductus arteriosus flow develops cardiac
murmur after the birth, despite the persistent ductus arteriosus
(PDA) flow maybe more complicated [11]. Although physiologic fetal
systolic murmur is differentiated from pathologic cardiopathy by the
disappearance of murmur after birth, cardiac murmur of the fetus may
be a positive sign of a congenital heart disease in fetal heart screening.
Fortunately, all of fetal systolic murmur recorded in antepartum period
disappeared after birth in our studies, and therefore they were thought
to be physiologic and it may be caused by fetal ductus arteriosus flow. In
another view point, the murmur caused by fetal ductus arteriosus may
be caused wide directivity of heart sound microphone. The record of
fetal heart action with continuous wave (CW) ultrasonic Doppler fetal
heart detector (Doptone, Smith-Kline, USA) recorded various fetal
heart valve actions, but no blood flow through ductus arteriosus due
to the narrow and unidirectional ultrasound beam in the ultrasound
detector, i.e. the ultrasound beam would be radiated in the circle of 2
cm diameter covering fetal heart but not the ductus arteriosus [12],
while the wide directivity of a microphone might cover the blood flow
through ductus arteriosus at the same time with fetal heart valve action
forming I and II heart tones. Therefore, CW ultrasonic Doppler method
would be a differential diagnosis of physiological blood flow in the
ductus arteriosus.
References
Digital technique can be used in modern fPCG, i.e. single frequency
characteristics preamplifier output will be sampled with 2 ms interval
and stored in computer memory. Read-out fetal heart sound is shown
in computer display. Hard copy is printed out. Any analysis of the sound
is performed by the computer on the read-out data. Every thing will be
simplified by the computerized digital analysis.
Conclusion
Fetal heart sound auscultation should not be applied for the fetal
monitoring due its poor ability to detect FHR abnormalities. FHR was
recorded by instantaneous FHR meter with the single trigger formed
by two tones. Beat-to-beat FHR variation was recorded with fetal heart
sound too. The autocorrelation FHR meter rejected FHR tracing noises
Citation: Maeda K, Nakano H (2013) Systolic Fetal Heart Murmur Detected
in Fetal Phonocardiography. Occup Med Health Aff 1: 101. doi:10.4172/
omha.1000102
Occup Med Health Aff
ISSN:OMHA an open access journal
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